The field of the invention is that of the catalysis of reactions for the cationic polymerization and/or crosslinking of monomers, oligomers and/or polymers, comprising reactive functional radicals capable of forming intra-chain and inter-chain bridges, so as to obtain a polymerized and/or crosslinked composite material or coating which has a certain level of hardness and a certain level of mechanical strength.
More specifically, the subject of the present invention is novel initiator systems for cationic polymerization and/or crosslinking. These initiators comprise at least one onium borate and at least one cyclic compound allowing the initiation and progress of reactions for forming polymers and/or resins, starting with substrates formed from monomers, oligomers and/or polymers containing reactive organofunctional groups.
The reactions more particularly concerned are those in which cationic agents act as direct promoters of inter-chain and/or intra-chain bonding.
In general, these reactions take place by photochemical and/or thermal activation and/or by activation with a beam of electrons. As a practical example, the light energy of a UV radiation allows the formation of active protagonists, for example by cleaving bonds, and thus triggering of the polymerization and/or crosslinking reactions is effected.
In the present description, the polymers and/or resins obtained are prepared from monomers, oligomers and/or polymers which are either (1) of organic nature, in particular exclusively hydrocarbon-based, or (2) of polyorganosiloxane nature, and comprise organofunctional groups in their structure, for example groups such as epoxides, oxetanes and/or alkenyl ethers, which react cationically and with the aid of the novel initiator systems according to the invention which are described below. It is also possible to use (3) monomers, oligomers and/or polymers with acrylic groups, for example pure acrylic or methacrylic groups, which can be added to the cationic polymerization medium.
A subject of the present invention is thus also compositions comprising base materials (monomers, oligomers and/or polymers) which can be polymerized and/or crosslinked cationically, the initiator systems described below, and optionally one or more additives chosen from those generally known in the applications for which these compositions are intended.
For example, these compositions can be used to make coatings on objects such as solid articles or supports, in particular a paper support, a polymer film of polyester or polyolefin type, an aluminium support and/or a tinplate support.
Initiators for the polymerization and/or crosslinking, for example the photochemical polymerization and/or crosslinking, of monomers, oligomers and/or polymers comprising reactive organofunctional groups in their structure are described in EP-0 562 897 in the name of the Applicant. The initiator salts in that patent represent an appreciable technical advance over the initiators previously known, of onium salt type or of organometallic complex type, and in particular over those in which the anion of the initiator salt is SbF6xe2x88x92 which is one of the only types which is satisfactory in terms of catalytic performance, but which poses serious problems of use on account of the presence of heavy metals.
The initiator salts according to EP-A-0 562 897 are used, for example, for the preparation of coatings on paper starting with epoxidized monomers which are polymerized and crosslinked by UV irradiation. In order to assess the performance as initiator, the reactivity of the substrate/initiator couple and the speed of polymerization/crosslinking are evaluated, by means of the rate of throughput required to cure the layer coated onto the paper, as well as by means of the number of passages. The measured results are acceptable, but it nevertheless remains that, in order to satisfy the production efficiency requirements of the people using them, the initiator systems need to achieve higher and higher performance levels. They must thus make it possible to achieve polymerization/cross-linking reactivities and rates that are as high as possible, so as to be able to increase the coating rates.
Accordingly, one of the essential objects of the present invention is to satisfy the production efficiency requirements stated above.
Another essential object of the invention is to provide novel initiator systems which give high performance as initiators with respect to the majority of organofunctional monomers, oligomers and/or polymers which can be polymerized and/or crosslinked cationically; the monomers, oligomers and/or polymers being in particular (1) of organic nature, preferably exclusively hydrocarbon-based, or (2) of polyorganosiloxane nature, optionally as a mixture (3) with other monomers, oligomers and/or polymers containing acrylic groups.
Another essential object of the invention is to provide cationic initiator systems which are effective in small amount, but which are also easy to handle and relatively non-toxic, and which consequently make it possible to obtain composite coatings and/or materials which do not yellow over time and/or after curing.
Another object of the invention is to provide compositions of organofunctional monomers, oligomers and/or polymers which can be crosslinked cationically and under photonic and/or thermal activation and/or under activation with a beam of electrons.
Another object of the invention is to provide compositions of this type which can be used either as a thin layer, the thickness of which is, for example, in the range from 0.1 to 1 xcexcm, or as a thicker layer, the thickness of which is, for example, in the range from a value of greater than one micrometer to several centimeters.
Another object of the invention is to provide compositions of this type for the preparation of a composite material.
These various objects are achieved by the invention which firstly relates, in its first subject, to novel initiator systems comprising at least one carefully selected onium borate and at least one carefully selected cyclic compound. Thus, the initiator system for polymerization and/or crosslinking comprises:
(1) at least one onium borate in which:
(i) the cationic species is chosen from the onium salts of formula (I)
[(R1)nxe2x88x92Ixe2x88x92(R2)m]+xe2x80x83xe2x80x83(I)
xe2x80x83in which formula:
the radicals R1, which may be identical or different, represent a carbocyclic or heterocyclic C6-C20 aryl radical, it being possible for the said heterocyclic radical to contain nitrogen and/or sulphur as hetero elements,
the radicals R2, which may be identical or different, represent R1, a linear or branched C1-C30 alkyl radical or a linear or branched C1-C30 alkenyl radical,
the said radicals R1 and R2 optionally being substituted with:
a linear or branched C1-C25 alkyl group,
an alkoxy group OR13
a ketone group xe2x80x94(Cxe2x95x90O)xe2x80x94R13,
an ester or carboxylic group xe2x80x94(Cxe2x95x90O)xe2x80x94Oxe2x80x94R113,
a mercapto group SR13,
a mercapto group SOR13,
R13 being a radical chosen from the group consisting of a hydrogen atom, a linear or branched C1-C25 alkyl radical, a C6-C30 aryl radical and an alkylaryl radical in which the alkyl portion is linear or branched and C1-C25 and the aryl portion is C6-C30,
a nitro group,
a chlorine atom,
a bromine atom, and/or
a cyano group,
n is an integer ranging from 1 to v+1, v being the valency of iodine,
m is an integer with n+m=v+1;
(ii) and in that the anionic borate species has the formula (II):
[BXaR3b]xe2x88x92xe2x80x83xe2x80x83(II)
xe2x80x83in which:
a and b are integers such that 0xe2x89xa6axe2x89xa64, 0xe2x89xa6bxe2x89xa64, and a+b=4,
the symbols X, which may be identical or different, represent:
a halogen atom chosen from chlorine and/or fluorine with 0xe2x89xa6axe2x89xa63,
an OH function with 0xe2x89xa6axe2x89xa62, and
the radicals R3, which may be identical or different, represent:
a phenyl radical substituted with at least one electron-withdrawing group such as xe2x80x94CF3, xe2x80x94OCF3, xe2x80x94NO2, xe2x80x94CN, xe2x80x94SO2R14, xe2x80x94O(Cxe2x95x90O)xe2x80x94R14, xe2x80x94Oxe2x80x94CnF2n+1, xe2x80x94CnF2n+1, n being an integer between 1 and 20, or substituted with at least two halogen atoms, in particular fluorine atoms,
an aryl radical containing at least two aromatic nuclei, such as biphenyl or naphthyl, optionally substituted with at least one halogen atom, in particular a fluorine atom, or with an electron-withdrawing group such as xe2x80x94CF3, xe2x80x94OCF3, xe2x80x94NO2, xe2x80x94CN, xe2x80x94SO2R14, xe2x80x94O(Cxe2x95x90O)xe2x80x94R14, R14 being xe2x80x94Oxe2x80x94CnF2n+1, xe2x80x94CnF2+1, n being an integer between 1 and 20;
(2) and at least one cyclic compound corresponding to one of the formulae (III) to (VI) below: 
xe2x80x83in which:
when n 1, Ar1 represents an aryl radical containing from 6 to 18 carbon atoms, a tetrahydronaphthyl, thienyl, pyridyl or furyl radical or a phenyl radical bearing one or more substituents chosen from the group consisting of F, Cl, Br, CN, OH, linear or branched C1-C12 alkyls, xe2x80x94CF3, xe2x80x94OR6, xe2x80x94Ophenyl, xe2x80x94SR6, xe2x80x94Sphenyl, xe2x80x94SO2phenyl, xe2x80x94COOR6, xe2x80x94Oxe2x80x94(CH2xe2x80x94CHxe2x95x90CH2), xe2x80x94O(CH2H4xe2x80x94O)mxe2x80x94H, xe2x80x94O(C3H6O)mxe2x80x94H, m being between 1 and 100,
when n=2, Ar1 represents a C6-C12 arylene radical or a phenylene-T-phenylene radical, in which T represents xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94 or xe2x80x94CH2xe2x80x94,
X represents a group xe2x80x94OR7 or xe2x80x94OSiR8(R9)2 or forms, with R4 a group xe2x80x94Oxe2x80x94CH(R10)xe2x80x94,
R4 represents a linear or branched C1-C8 alkyl radical which is unsubstituted or bears a group xe2x80x94OH, xe2x80x94OR6, C2-C8 acyloxy, xe2x80x94COOR6, xe2x80x94CF3 or xe2x80x94CN, a C3 or C4 alkenyl radical, a C6 to C18 aryl radical or a C7 to C9 phenylalkyl radical,
R5 has one of the meanings given for R4 or represents a radical xe2x80x94CH2CH2R11, or alternatively forms, with R4, a C2-C8 alkylene radical or a C3-C9 oxa-alkylene or aza-alkylene radical,
R6 represents a lower alkyl radical containing from 1 to 12 carbon atoms,
R7 represents a hydrogen atom, a C1-C12 alkyl radical, a C2-C6 alkyl radical bearing a group xe2x80x94OH, xe2x80x94OR6 or xe2x80x94CN, a C3-C6 alkenyl radical, a cyclohexyl or benzyl radical, a phenyl radical optionally substituted with a chlorine atom or a linear or branched C1-C12 alkyl radical or a 2-tetrahydropyranyl radical,
R8 and R9 are identical or different and each represent a C1-C4 alkyl radical or a phenyl radical,
R10 represents a hydrogen atom, a C1-C8 alkyl radical or a phenyl radical,
R11 represents a radical xe2x80x94CONH2, xe2x80x94CONHR6, xe2x80x94CON(R6)2, xe2x80x94P(O)(OR6)2 or 2-pyridyl; 
xe2x80x83in which:
Ar2 has the same meaning as Ar1 in formula (III) in the case in which n=1,
R15 represents a radical chosen from the group consisting of a radical Ar2, a radical xe2x80x94(Cxe2x95x90O)xe2x80x94Ar2, a linear or branched C1-C12 alkyl radical, a C6-C12 cycloalkyl radical and a cycloalkyl radical forming a C6-C12 ring with the carbon of the ketone or a carbon of the radical Ar2, it being possible for these radicals to be substituted with one or more substituents chosen from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94CN, xe2x80x94OH, xe2x80x94CF3, xe2x80x94OR6, xe2x80x94SR6, xe2x80x94COOR6, linear or branched C1-C12 alkyl radicals optionally bearing a group xe2x80x94OH, xe2x80x94OR and/or xe2x80x94CN; and linear or branched C1-C8 alkenyl radicals; 
xe2x80x83in which
Ar3 has the same meaning as Ar1 in formula (III) in the case in which n=1,
R16, which may be identical or different, represent a radical chosen from the group consisting of a radical Ar3, a radical xe2x80x94(Cxe2x95x90O)xe2x80x94Ar3, a linear or branched C1-C12 alkyl radical, a C6-C12 cycloalkyl radical, it being possible for these radicals to be substituted with one or more substituents chosen from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94CN, xe2x80x94OH, xe2x80x94CF3, xe2x80x94OR6, xe2x80x94SR6, xe2x80x94COOR6, linear or branched C1-C12 alkyl radicals optionally bearing a group xe2x80x94OH, xe2x80x94OR6 and/or xe2x80x94CN, and linear or branched C1-C8 alkenyl radicals; 
xe2x80x83in which:
R5, which may be identical or different, have the same meanings as in formula (III),
Y, which may be identical or different, represent X and/or R4,
Z represents:
a direct bond,
a C1-C6 divalent alkylene radical, or a phenylene, diphenylene or phenylene-T-phenylene radical, or alternatively forms, with the two substituents R5 and the two carbon atoms bearing these substituents, a cyclopentane or cyclohexane nucleus,
a divalent group xe2x80x94Oxe2x80x94R12xe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94SiR8R9xe2x80x94Oxe2x80x94SiR8R9xe2x80x94Oxe2x80x94 or xe2x80x94Oxe2x80x94SiR8R9xe2x80x94Oxe2x80x94,
R12 represents a C2-C8 alkylene, C4-C6 alkenylene or a xylylene radical, and
Ar4 has the same meaning as Ar1 in formula (III) in the case in which n=1.
Advantageously, the anionic species of the onium salt is chosen from the following species, alone or as a mixture, of formula: [B(C6F5)4]xe2x88x92, [B(C6H3(CF3)2)4]xe2x88x92, [B(C6H4OCF3)4]xe2x88x92, [B(C6H4CF3)4]xe2x88x92, [(C6F5)2BF2]xe2x88x92, [C6F5BF3]xe2x88x92, [B(C6H3F2)4]xe2x88x92.
More particularly, the anionic species of the onium salt is chosen from the following species, alone or as a mixture, of formulae: [B(C6F5)4]xe2x88x92, [B(C6H3(CF3)2)4]xe2x88x92, [B(C6H4OCF3)4]xe2x88x92.
For the cationic species of the onium borate, this will advantageously be chosen from the group consisting of:
[(C6H5)2I]+, [C8H17xe2x80x94Oxe2x80x94C6H5xe2x80x94Ixe2x80x94C6H5]+,
[C12H25xe2x80x94C6H5xe2x80x94Ixe2x80x94C6H5]+, [(C8H17xe2x80x94Oxe2x80x94C6H5)2I]+,
[(C8H17)xe2x80x94Oxe2x80x94C6H5xe2x80x94Ixe2x80x94C6H5)]+, [(C12H25xe2x80x94C6H5)2I]+,
[(CH(CH3)2xe2x80x94C6H5)xe2x80x94Ixe2x80x94C6H5xe2x80x94CH3]+, [C6H4xe2x80x94Oxe2x80x94C6H4xe2x80x94Ixe2x80x94C6H4]+,
[C6H4xe2x80x94(Cxe2x95x90O)xe2x80x94C6H4xe2x80x94Ixe2x80x94C6H4]+,
[C6H4xe2x80x94Oxe2x80x94C6H4xe2x80x94Ixe2x80x94C6H4xe2x80x94Oxe2x80x94C6H4]+,
[C6H4xe2x80x94(Cxe2x95x90O)xe2x80x94C6H4xe2x80x94Ixe2x80x94C6H4xe2x80x94(Cxe2x95x90O)xe2x80x94C6H4]30 ,
[C6H4xe2x80x94Ixe2x80x94C6H4xe2x80x94Oxe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94Oxe2x80x94CH(OH)xe2x80x94C12H25]+, and a mixture thereof.
The onium borates which form the subject of the present invention can be prepared by exchange reaction between a salt of the cationic species (halide such as, for example, chloride or iodide) with an alkali metal salt of the anionic species (sodium, lithium or potassium).
The operating conditions (respective amounts of reagents, choice of solvents, duration, temperature, stirring) are within the scope of a person skilled in the art; these conditions should make it possible to recover the desired onium borate in solid form by filtering off the precipitate formed, or in oily form by extraction using a suitable solvent.
The operating conditions for synthesizing the halides of the cationic species of formula (I) are known per se. In this respect, reference will be made in particular to patent EP-0 562 897 in the name of the Appplicant.
The procedures for synthesizing the alkali metal salts of the anionic species (II) are also known per se; especially, for example, in patent EP-0 562 897 in the name of the Applicant.
In the context of the invention, many types of cyclic compounds can be used in combination with the onium borate. In this respect, the type of cyclic compound which is used and preferred will depend on the envisaged used, i.e., for example, in the case of activation by UV, its maximum or maxima of absorption of UV light is (are) adapted to the type of application envisaged.
For example, when the composition to be crosslinked and/or polymerized contains white pigments which absorb in the UV range, a cyclic compounds which has a maximum absorption of light in the visible range will be selected.
In the case of a use for the manufacture of transparent organic and/or silicone paint under UV activation, a cyclic compound whose maximum absorption is superposable with the emission lines of the UV lamp will be chosen.
As examples of cyclic compounds, mention will be made in particular of the following products, alone or as a mixture:
9-xanthenone; 1,4-dihydroxyanthraquinone; anthraquinone; 2-methylanthraquinone,
2,2xe2x80x2-bis(3-hydroxy-1,4-naphthoquinone);
2,6-dihydroxyanthraquinone; 1-hydroxycyclohexyl phenyl ketone; 1,5-dihydroxyanthraquinone; 1,3-diphenyl-1,3-propanedione;
5,7-dihydroxyflavone; dibenzoyl peroxide;
2-benzoylbenzoic acid; 2-hydroxy-2-methylpropiophenone; 2-phenylacetophenone;
2,4,6-trimethylbenzoyldiphenylphosphine oxide; anthrone; bis(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide;
poly[1,4-benzenedicarbonyl-alt-bis(4-phenoxyphenyl)methanone]; 
Preferably, the cyclic compound(s) is (are) chosen from the group consisting of:
4,4xe2x80x2-dimethoxybenzoin; phenanthrenequinone;
2-ethylanthraquinone; 2-methylanthraquinone;
1,8-dihydroxyanthraquinone; dibenzoyl peroxide;
2,2-dimethoxy-2-phenylacetophenone; benzoin;
2-hydroxy-2-methylpropiophenone;
4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone; 
xe2x80x83benzoylacetone; 
xe2x80x83and a mixture thereof.
As examples of commercial cyclic products, mention may be made of the products sold by the company Ciba-Geigy: Irgacure 369, Irgacure 651, Irgacure 907, Darocure 1173, etc.
The initiator systems according to the invention can be used as they are obtained after the process for preparing them, for example in solid or liquid form or as a solution in a suitable solvent, in compositions of monomers, oligomers and/or polymers which are intended to be polymerized and/or crosslinked cationically and under activation, for example UV activation.
Thus, according to another of its aspects, the invention relates, in its second subject, to compositions comprising at least one matrix based on a monomer, an oligomer and/or a polymer which can be polymerized-and/or crosslinked cationically, a catalytically effective amount of at least one initiator system of the type in accordance with the invention and described above, optionally a polymerization and/or crosslinking accelerator, and optionally also one or more additives chosen from those generally known in the applications for which these compositions are intended.
According to the invention, the expression xe2x80x9ceffective catalytic amount of initiatorxe2x80x9d means an amount which is sufficient to initiate the polymerization and/or the crosslinking. This amount is generally between 0.01 and 20 parts by weight, usually between 0.05 and 8 parts by weight, to polymerize and/or crosslink 100 parts by weight of the matrix. In the initiator system according to the invention, the onium borate/cyclic compound weight ratio is between 0.1 and 10.
According to a first advantageous provision of the invention taken in its second subject, the polymerizable and/or crosslinkable composition is based on monomer(s) and/or oligomer(s) and/or polymer(s) of organic nature belonging to at least one of the following organic species:
xcex11.1 cycloaliphatic epoxides, taken alone or as a mixture with each other;
epoxides such as 3,4-epoxycyclohexylmethyl 3xe2x80x2,4-epoxycyclohexanecarboxylate: 
or bis(3,4-epoxycyclohexyl) adipate, being particularly preferred;
xcex11.2 non-cycloaliphatic epoxides, taken alone or as a mixture with each other;
epoxides of the type resulting from the coupling of Bisphenol A and epichlorohydrin and of the type:
di- and triglycidyl ethers of alkoxylated Bisphenol A, of 1,6-hexanediol, of glycerol, of neopentyl glycol and of trimethylolpropane,
or Bisphenol A diglycidyl ethers,
xcex1-olefin epoxides, Novolac epoxide, epoxidized soybean oil and flax oil, epoxidized polybutadiene and, more generally, an epoxidized and monohydroxylated, saturated or unsaturated diene polymer, described in patent application WO-A-96/11215 (the content of which is incorporated in its entirety by way of reference), obtained by epoxidizing a base diene polymer of formula:
(HO)xxe2x80x94Jxe2x80x94Lzxe2x80x94Kxe2x80x94(OH)y or (HO)xxe2x80x94Jxe2x80x94Kxe2x80x94Lxe2x80x94(OH)y
xe2x80x83in which:
the symbols J and K represent sequences or blocks consisting of: homopolymers obtained by polymerizing a conjugated diene monomer containing from 4 to 24 carbon atoms (such as, for example: 1,3-butadiene, isoprene or 2-methyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene); copolymers obtained by copolymerizing at least two of the abovementioned conjugated dienes with each other; or copolymers obtained by copolymerizing at least one of the abovementioned conjugated dienes with at least one ethylenically unsaturated monomer chosen from aromatic vinyl monomers containing from 8 to 20 carbon atoms (such as, for example: styrene, ortho-, meta- or para-methylstyrene, vinylmesitylene, vinylnaphthalene);
the symbol L represents a polymer sequence or block obtained from the abovementioned aromatic vinyl monomers;
x and y are numbers equal to zero or 1, x being equal to zero when y=1 and x being equal to 1 when y=0; and z is a number equal to zero or 1;
it being possible for the said base diene polymer, on the one hand before epoxidation, to be partially saturated by hydrogenation, and, on the other hand after epoxidation, to contain from 0.1 to 7 milliequivalents of epoxy function per gram of epoxidized and monohydroxylated diene polymer [as examples of epoxidized and monohydroxylated diene polymers mention will be made of the species obtained by epoxidizing the following base diene polymers: Isxe2x80x94Buxe2x80x94OH, Isxe2x80x94St/Buxe2x80x94OH, Isxe2x80x94EtBuxe2x80x94OH or Isxe2x80x94St/EtBuxe2x80x94OH, in which: the symbol Is is a polyisoprene block, the symbol Bu is a polybutadiene block, the symbol EtBu is a poly(ethylene-butylene) block (derived from the selective hydrogenation of a polybutadiene block), the symbol St is a polystyrene block (the St/Bu assembly representing a block based on a random copolymer obtained by copolymerizing 1,3-butadiene and styrene), and OH is a hydroxyl group (the xe2x80x94EtBuxe2x80x94OH assembly meaning, for example, that the hydroxyl-group donor is attached to the hydrogenated polybutadiene block)],
being particularly preferred;
xcex12 linear or cyclic alkenyl ethers, taken alone or as a mixture with each other:
vinyl ethers, in particular triethylene glycol divinyl ether, cyclic vinyl ethers or tetramers and/or dimers of acroleins, and the vinyl ether of the following formula: 
propenyl ethers, and
butenyl ethers being more especially preferred,
xcex13 polyols, taken alone or as a mixture with each other, and preferably the compound of formula below, I being greater than 1 and less than 100: 
xe2x80x83in which R16 is a linear or branched C1-C30 alkyl radical.
According to a second advantageous provision of the invention, taken in its second subject, the polymerizable and/or crosslinkable composition is based on monomer(s) and/or oligomer(s) and/or polymer(s) of polyorganosiloxane nature consisting of units of formula (VII) and ending with units of formula (VIII), or of cyclic nature consisting of units of formula (VII), which are represented below: 
in which:
the symbols R17 are identical or different and represent:
a linear or branched alkyl radical containing 1 to 8 carbon atoms, optionally substituted with at least one halogen, preferably fluorine, the alkyl radicals preferably being methyl, ethyl, propyl, octyl and 3,3,3-trifluoropropyl,
a cycloalkyl radical containing between 5 and 8 optionally substituted cyclic carbon atoms,
an aryl radical containing between 6 and 12 carbon atoms which may be substituted, preferably phenyl or dichlorophenyl,
an aralkyl radical with an alkyl portion containing between 5 and 14 carbon atoms and an aryl portion containing between 6 and 12 carbon atoms, optionally substituted on the aryl portion with halogens, alkyls and/or alkoxys containing 1 to 3 carbon atoms,
the symbols Yxe2x80x2 are identical or different and represent:
the group R17,
a hydrogen radical,
and/or an organofunctional group which can be crosslinked cationically, preferably an epoxy-functional and/or vinyloxy-functional group, connected to the silicon of the polyorganosiloxane via a divalent radical containing from 2 to 20 carbon atoms which can contain at least one hetero atom, preferably oxygen, and
at least one of the symbols Yxe2x80x2 representing a functional organic group which can be crosslinked cationically; and
the symbol R16, which may be identical or different, represents a radical selected from the group consisting of a radical Ar3, a radical xe2x80x94(Cxe2x95x90O)xe2x80x94Ar3, a linear or branched C1-C12 alkyl radical, a C6-C12 cycloalkyl radical, wherein said radical is optionally substituted with one or more substituents selected from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94CN, xe2x80x94OH, xe2x80x94CF3, OR6, xe2x80x94SR6, xe2x80x94COOR6, linear or branched C1-C12 alkyl radicals optionally bearing a group xe2x80x94OH, xe2x80x94OR6, and/or xe2x80x94CN, and linear or branched C1-C8 alkenyl radicals.
According to one advantageous variant of the invention, at least one of the symbols R17 of the polyorganosiloxanes used in the context of the invention as monomer(s), oligomer(s) or polymer(s) represents a phenyl, tolyl or dichlorophenyl radical.
According to another advantageous variant of the invention, the polyorganosiloxanes used comprise from 1 to 10 organofunctional groups per mole. For an epoxy-functional group, this corresponds to epoxide contents ranging from 20 to 2000 molar meq/100 g of polyorganosiloxane.
The linear polyorganosiloxanes can be oils with a dynamic viscosity at 25xc2x0 C. of about 10 to 10,000 mPaxc2x7s at 25xc2x0 C., generally from about 50 to 5000 mPaxc2x7s at 25xc2x0 C. and even more preferably from 100 to 600 mPaxc2x7s at 25xc2x0 C., or gums with a molecular mass of about 1,000,000.
When the polyorganosiloxanes are cyclic, they consist of units (VII) which can be, for example, of the dialkylsiloxy or alkylarylsiloxy type. These cyclic polyorganosiloxanes have a viscosity of about 1 to 5000 mPaxc2x7s.
As examples of divalent radicals linking an organofunctional group of the epoxy type, mention may be made of those included in the following formulae: 
As regards organofunctional groups of the alkenyl ether type, mention may be made of those contained in the following formulae:
xe2x80x94(CH2)3xe2x80x94Oxe2x80x94CHxe2x95x90CH2; xe2x80x94(CH2)3xe2x80x94Oxe2x80x94R18xe2x80x94Oxe2x80x94CHxe2x95x90CH2; xe2x80x94(CH2)3xe2x80x94Oxe2x80x94CHxe2x95x90CHxe2x80x94R19
in which:
R18 represents:
an optionally substituted, linear or branched C1-C12 alkylene radical, or
a C5-C12 arylene radical, preferably a phenylene radical, which is optionally substituted, preferably with one to three C1-C6 alkyl groups,
R19 represents a linear or branched C1-C6 alkyl radical.
According to a third other advantageous provision of the invention, taken in its second subject, the polymerizable and/or crosslinkable composition is based on monomer(s) and/or oligomer(s) and/or polymer(s), of polyorganosiloxane nature and of organic nature, in particular hydrocarbon-based.
According to a fourth other advantageous provision of the invention, taken in its second subject, the polymerizable and/or crosslinkable composition is based on monomner(s) and/or oligomer(s) and/or polymer(s), of polyorganosiloxane nature and/or of organic nature, in particular hydrocarbon-based, and also comprises monomers, oligomers and/or polymers containing organofunctional groups of acrylate species; and in particular epoxidized acrylates, acrylo-glycero-polyester, multifunctional acrylates, acrylo-urethanes, acrylo-polyethers, acrylo-polyesters, unsaturated polyesters and acrylo-acrylics.
These acrylic species, optionally as a mixture, which can be used with monomer(s) and/or oligomer(s) and/or polymer(s) of polyorganosiloxane nature and/or of organic nature, are preferably chosen from the following species: trimethylolpropane triacrylate, tripropylene glycol diacrylate, glycidylpropyl triacrylate, pentaerythrityl triacrylate, trimethylolpropane ethoxylate triacrylate, Bisphenol A ethoxylate diacrylate, tripropylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyether acrylates, polyester acrylates (for example the product Ebecryl 810 from the company UCB-Radcure) and epoxy acrylates (for example the product Ebecryl 600 from the company UCB-Radcure).
It is recalled that, in the present specification, the expression xe2x80x9cacrylicxe2x80x9d encompasses compounds comprising the function of the type CH2xe2x95x90CHxe2x80x94COOxe2x80x94 or of the type CH2xe2x95x90C(CH3)xe2x80x94COOxe2x80x94.
Conventionally, the compositions according to the invention, taken in its second subject, can also comprise one or more additives chosen as a function of the final intended application.
When the polymerizable and/or crosslinkable composition is based on at least one of the organic species xcex11.1 to xcex13, optionally as a mixture with monomers, oligomers and/or polymers of acrylic nature, the additives can especially be compounds optionally in the form of polymers, with labile hydrogens, such as alcohols, glycols and polyols, which are useful for improving the flexibility of the cured material after polymerization and/or crosslinking; mention may be made, for example, of polycaprolactone-polyols, in particular the polymer obtained from 2-ethyl-2-(hydroxymethyl)-1,3-propanediol and from 2-oxepanone, such as the product Ton Polyol-301 sold by the company Union Carbide, or the other commercial polymers Tone Polyol 201 and Tone Polyol 12703 from the company Union Carbide. In addition, in this case, additives which may be mentioned are diacids containing a long alkyl chain, epoxidized or non-epoxidized unsaturated fatty acid esters, for example epoxidized soybean oil or epoxidized flax oil, the epoxidized 2-ethylhexyl ester, 2-ethylhexyl epoxystearate, octyl expoxystearate, epoxidized acrylic esters, epoxidized soybean oil acrylates, epoxidized flax oil acrylates, polypropylene glycol diglycidyl ether, epoxides containing long aliphatic chains, etc.
They may also be, irrespective of the nature of the polymerizable matrix, for example: mineral fillers such as, in particular, ground synthetic (polymer) or natural fibres, calcium carbonate, talc, clay, titanium dioxide, precipitation or combustion silica; photosensitizers, in particular based on thioxanthone (for example: isopropylthioxanthone, diethylthioxanthone and 1-chloro-4-propoxythio-xanthone); soluble dyes; oxidation inhibitors and corrosion inhibitors; organosilicon or non-organosilicon adhesion modifiers; fungicidal, bactericidal or antimicrobial agents; and/or any other material which does not interfere with the catalytic activity of the initiator and which does not absorb in the wavelength range chosen for the photoactivation.